Prevent accidental partial name matching in editable hooks

changelog.d/3561.misc.rst

@@ -0,0 +1 @@
+Fix accidental name matching in editable hooks.

setuptools/command/editable_wheel.py

@@ -758,7 +758,7 @@ class _EditableFinder:  # MetaPathFinder
     @classmethod
     def find_spec(cls, fullname, path=None, target=None):
         for pkg, pkg_path in reversed(list(MAPPING.items())):
-            if fullname.startswith(pkg):
+            if fullname == pkg or fullname.startswith(f"{{pkg}}."):
                 rest = fullname.replace(pkg, "", 1).strip(".").split(".")
                 return cls._find_spec(fullname, Path(pkg_path, *rest))
 

setuptools/tests/test_editable_install.py

@@ -515,6 +515,30 @@ def test_no_recursion(self, tmp_path):
             with pytest.raises(ImportError, match="pkg"):
                 import_module("pkg")
 
+    def test_similar_name(self, tmp_path):
+        files = {
+            "foo": {
+                "__init__.py": "",
+                "bar": {
+                    "__init__.py": "",
+                }
+            },
+        }
+        jaraco.path.build(files, prefix=tmp_path)
+
+        mapping = {
+            "foo": str(tmp_path / "foo"),
+        }
+        template = _finder_template(str(uuid4()), mapping, {})
+
+        with contexts.save_paths(), contexts.save_sys_modules():
+            sys.modules.pop("foo", None)
+            sys.modules.pop("foo.bar", None)
+
+            self.install_finder(template)
+            with pytest.raises(ImportError, match="foobar"):
+                import_module("foobar")
+
 
 def test_pkg_roots(tmp_path):
     """This test focus in getting a particular implementation detail right.